The invention relates to a communication device, comprising a star circuit whereto a variable number of electrical bus connections with stations coupled thereto can be connected in order to form, by way of the assembly of bus connections, a bus organization for digital communication signals between the assembly of stations.
Generally, electrical bus connections should be electrically terminated at both ends by means of a characteristic impedance. When a number of stations are connected to an electrical bus connection and each of these stations possesses two connections for the electrical bus connection, these stations can be included in the communication device by the so-called looping through of the connections in the stations. In that case, the stations at the ends of the electrical bus connection in principle have a free connection where the electrical bus connection should be terminated. When a number of stations with a star circuit are connected to electrical bus connections, looping through does not take place and each station should be electrically terminated at the free connection, that is to say by means on a characteristic impedance which is dependent of the entire communication device with the connected stations. In order to avoid this system-dependent termination, each bus connection should be electrically terminated at the input of the station connected thereto. The communication device with the star circuit then comprises as many parallel terminating impedances as there are stations connected to the communication device. The impedance configuration is then again dependent on the number of stations, so that the operation of the communication device may be affected.